A tank at America's most contaminated nuclear site is leaking radioactive liquids, raising concerns about the integrity of other storage facilities at the Hanford Nuclear Reservation in Washington state.

Officials say the single-shell tank could be leaking up to 1,135 liters per year, creating a long-term threat that could impact groundwater or rivers.

Washington state Governor Jay Inslee said Friday, "we were told this problem was dealt with years ago."

A cleanup of the site would cost billions of dollars and last decades.

The tank holds nearly 1.7 million liters of sludge, the radioactive by-product of decades of plutonium production for nuclear weapons.

Authorities say the tank is the first confirmed leak since all Hanford tanks were stabilized in 2005.

The facility was created during World War II for plutonium production when the country was secretly building an atomic bomb.